1. Field of the Invention
The present invention relates to a semiconductor device using a semiconductor nanowire.
Also, the present invention relates to a semiconductor device which has both a PN or PIN junction device and a field effect transistor using a semiconductor nanowire. Further, the present invention relates to a display apparatus and an image pick-up apparatus using the semiconductor device.
2. Description of the Related Art
A semiconductor nanowire is a wire exhibiting semiconductor characteristics and having a structure of a diameter of about several hundred nanometers or less. Such a semiconductor nanowire is manufactured using, for example, a vapor-liquid-solid (VLS) mechanism.
The VLS mechanism is a method in which metal fine particles on a substrate and the substrate or a desired element form a molten compound alloy, which decomposes a raw material gas to allow a nanowire to grow. The VLS mechanism is known as a method of synthesizing nanowires, various kinds of carbon nanotubes, and oxide whiskers. A semiconductor nanowire manufactured by the above-mentioned method exhibits a very high mobility of several hundred cm2/Vs to several thousand cm2/Vs. Therefore, it is possible to use the above-mentioned semiconductor nanowire in a field effect transistor (FET) which uses the semiconductor nanowire as its channel, and various studies are made for putting the semiconductor nanowire to practical use (for example, U.S. Pat. No. 6,872,645).
In U.S. Pat. No. 6,872,645, nanowire field effect transistors are manufactured by dispersing the above-mentioned semiconductor nanowires in a solvent and orienting the semiconductor nanowires on a substrate by fluid force. In the manufacturing method disclosed in U.S. Pat. No. 6,872,645, because a transistor can be manufactured in a coating process, a TFT having a high mobility and a large area can be manufactured.
Although a conventional silicon or compound semiconductor transistor has a high mobility, it is difficult to make a large-area transistor because a large-area substrate is difficult to be prepared or a vacuum apparatus is required. On the other hand, in a case of an organic transistor, while a large-area transistor can be manufactured because constraints on the substrate is not so strict and a coating process can be used, the mobility is as low as 0.1 cm2/Vs or less, which limits uses thereof.
The above-mentioned semiconductor nanowire transistor can solve both of the above-mentioned problems of a transistor at the same time, and thus, a TFT of a large-area and a low cost, and having flexibility or the like can be materialized with performance of an inorganic transistor maintained. Therefore, it can be used for a TFT for an organic EL display, a sheet computer, and the like, and has a potential of becoming a strong tool for creating a novel electronics device.
On the other hand, with regard to the above-mentioned semiconductor nanowire, a semiconductor nanowire 200 having a PN junction therein as illustrated in FIG. 10 is reported (see, for example, U.S. Pat. No. 6,882,051). U.S. Pat. No. 6,882,051 proposes applications to an LED, a solar cell, and a thermoelectric device by utilizing the PN junction in the nanowire.
Because an inorganic LED has a very high efficiency of 10 lm/W to 100 lm/W as compared with that of an organic EL device, and has a lifetime as long as several ten thousand hours, it is already put to practical use for various kinds of lighting and the like.
In the field of solar cells, studies on organic solar cells and dye-sensitized solar cells are carried out, but efficiencies thereof are lower than that of inorganic solar cells such as silicon solar cells and compound semiconductor solar cells. Thus, only the inorganic solar cells are put to practical use.
However, although the efficiency and lifetime of the inorganic LEDs and inorganic solar cells described above are already enough for practical use, because there are constraints on the substrate and a vacuum process is required, it is difficult to manufacture a large-area and low-cost device. Therefore, with regard to the area and the cost, the inorganic LEDs and inorganic solar cells are inferior to organic EL devices, organic solar cells, and dye-sensitized solar cells.
Thus, in U.S. Pat. No. 6,882,051, the semiconductor nanowire 200 is located on a substrate 201 as illustrated in FIG. 11, and is sandwiched between a pair of electrodes 202 to manufacture a device. By manufacturing a device having such the structure, a large-area and low cost semiconductor device can be manufactured with performance of an inorganic device maintained, and there is a potential for supplying, for example, a large-area lighting or solar cell at a low cost.